to be under an obligation (used as an auxiliary, typically in an interrogative or in a negative statement, and followed by infinitive, in certain cases without to; in the 3d person singular the form is need, not needs):

2, 3. See lack. 3. requirement. 4. Need,necessity imply a want, a lack, or a demand, which must be filled. Need, a word of Old English origin, has connotations that make it strong in emotional appeal: the need to be appreciated.Necessity, a word of Latin origin, is more formal and impersonal or objective; though much stronger than need in expressing urgency or imperative demand, it is less effective in appealing to the emotions: Water is a necessity for living things.5. emergency. 7. neediness, indigence, penury, privation. See poverty. 8. want, lack.

need

/niːd/

verb

1.

(transitive) to be in want of: to need money

2.

(transitive) to require or be required of necessity (to be or do something); be obliged: to need to do more work

3.

(takes an infinitive without to) used as an auxiliary in negative and interrogative sentences to express necessity or obligation, and does not add -s when used with he, she, it, and singular nouns: need he go?

4.

(intransitive) (archaic) to be essential or necessary to: there needs no reason for this

noun

5.

the fact or an instance of feeling the lack of something: he has need of a new coat

6.

a requirement: the need for vengeance

7.

necessity or obligation resulting from some situation: no need to be frightened

The more common Old English word for "need, necessity, want" was ðearf, but they were connected via a notion of "trouble, pain," and the two formed a compound, niedðearf "need, necessity, compulsion, thing needed." Nied also might have been influenced by Old English neod "desire, longing," which often was spelled the same. Common in Old English compounds, e.g. niedfaru "compulsory journey," a euphemism for "death;" niedhæmed "rape," the second element being an Old English word meaning "sexual intercourse;" niedling "slave." Meaning "extreme poverty, destitution" is from c.1200.

v.

Old English neodian "be necessary, be required (for some purpose); require, have need of," from the same root as need (n.). Meaning "to be under obligation (to do something)" is from late 14c. Related: Needed; needing. The adjectival phrase need-to-know is attested from 1952. Dismissive phrase who needs it?, popular from c.1960, is a translated Yiddishism.